Device for the ejection of pressings out of a press tool

ABSTRACT

Arrangement for the ejection of a pressed component from a press tool. The arrangement consists of a number of ejection pins distributed over the press surface tool. Each of the ejection pins is so arranged as to lie during the pressing operation with its tip no higher than on a level with the aforementioned press surface, and, in conjunction with the opening of the tool after a pressing operation has been completed, as to eject the component from the tool with its tip. A characteristic feature of the invention is that each ejection pin is operatively connected via a pistion rod to a hydraulic piston. The piston is capable of axial displacement in a hydraulic cylinder, which is filled with an incompressible fluid in space between the piston and an end wall of the cylinder. The space communicates via a duct with a drive unit for the ejection pin.

The present invention relates to an arrangement for the ejection of apressed component from a press tool consisting of a number of ejectionpins distributed over the press surface of the press tool, each of saidpins being so arranged as to lie during the pressing operation with itstip no higher than on a level with the aforementioned press surface,and, in conjunction with the opening of the tool after a pressingoperation has been completed, as to eject the component from the toolwith its tip.

A critical factor which governs the efficiency with which a press can beused is the speed at which a pressed component can be removed from thepress tool and new material can be introduced. The importance of theaforementioned operations being performed rapidly and with highprecision is further accentuated in multi-stage presses of the kindwhich are found, for example, in the automobile industry, in which afault in one of the pressing stages will prevent the execution of allthe other stages.

A large number of solutions have already been proposed to the problem ofrapidly achieving the ejection of the pressed component. In order to beable to guarantee that the surface finish of the components will not bedamaged by the ejection pins at the plate thicknesses which are nowcommon, it is necessary for the force exerted by each of these to berelatively small, that is to say a large number of ejection pins isrequired per unit of surface area. In the case of previously disclosedejection devices, at least two hydraulic lines are required for eachejection pin, and since the design of press tools has now becomeextremely complex, it has proved necessary, partly for reasons of space,to accept a reduction in the number of ejection pins.

The object of the present invention is to make available an ejectionarrangement of the kind referred to by way of introduction which willpermit the use of a sufficiently large number of ejection pins per unitof surface area of the press surface of the tool for the surface finishof the pressed component not to suffer damage on being ejected, butwithout jeopardizing the function of the press tool by the presence of alarge number of hydraulic lines for the ejection pins. This is permittedin accordance with the invention in that each ejection pin isoperatively connected via a piston rod to a hydraulic piston which iscapable of axial displacement in a hydraulic cylinder filled with anincompressible fluid in a space between the piston and an end wall ofthe cylinder, which space communicates via a duct with a drive unit forthe ejection pins, which unit consists of a number of mechanicallyinter-connected hydraulic cylinders with associated pistons whichcorresponds to the number of ejection pins, the piston rods of which areso arranged as to be carried in a synchronous fashion by the moving halfof the press tool, in conjunction with which the pistons are influencedby a spring device acting in the direction of ejection.

In accordance with a specific characteristic feature of the inventionthe cylinders are adjustable relative to a fixed reference for thepurpose of achieving synchronism between the ejection pins.

A preferred embodiment of the invention is characterized in accordancewith a second specific characteristic feature of the invention in thatthe hydraulic cylinder which interacts with the ejection pin is sealedagainst the corresponding piston rod, in that the space of the ejectioncylinder filled with incompressible fluid is defined not only by thepiston and the cylinder wall, but also by the end wall in which the sealagainst the piston rod is arranged, in that the duct is connected in anarea close to the aforementioned seal, in that the pistons of the driveunit are of the plunger type, and in that the aforementioned spring is agas spring which consists of a compressible fluid enclosed within aspace which is defined by the piston of the ejection pin, the walls andthe end wall of the hydraulic which interacts with the ejection pin atthe opposite end to the seal.

In accordance with a further characteristic feature of the invention analternative embodiment of the invention is characterized in that thespace of the ejection cylinder filled with an incompressible medium isdefined not only by the piston and the cylinder wall, but also by theuninterrupted end wall of the ejection cylinder, in that each duct isconnected to the cylinders of the drive unit for each ejection pin at orin the vicinity of the uninterrupted end wall of each cylinder, in thatthe piston rods of the drive unit are attached at their outer ends bymeans of a yoke, and in that the aforementioned spring, preferably ofthe gas type, is fixed between the yoke and the mechanicallyinter-connected cylinders in the drive unit and is so arranged, when thetool is opened, as to push the pistons into each cylinder in such a waythat the pressed component is ejected by the pins, and as to be overcomeby the pressing operation so that the ejection pins are brought to thesame level as the press surface.

The invention is described in more detail below with reference to theaccompanying drawing, in which

FIGS. 1a and 1b illustrate schematically in perspective view a preferredembodiment of an ejection arrangement in accordance with the inventionfor a pressed component, interacting with a press tool shown in itsclosed and open position respectively.

FIG. 1c illustrates schematically the construction of the ejectiondevice shown in FIGS. 1a and 1b.

FIGS. 2a, 2b and 2c show in a manner similar to FIGS. 1a, 1b and 1c analternative embodiment of the invention.

The designation 1 is used generally in the drawing in respect of a presstool with an upper, moving tool half 1a and a lower, fixed tool half 1b.The press tool is executed in a conventional fashion with raised andrecessed parts, which are not shown in the drawing, in order to producea component with the desired form.

The ejection arrangement consists of a number of ejection pins 2a, 2b,2c, . . . distributed in the lower tool half 1b of the press surface ofthe press tool 1, each pin constituting the outer part of a piston rodor being operatively connected to a hydraulic piston 16a, 16b, 16c, . .. , which piston is capable of axial displacement in an associatedcylinder 3a, 3b, 3c, . . . . Each hydraulic cylinder communicates via aduct 4a, 4b, 4c, . . . with a drive unit for the ejection pins 2a, 2b,2c, . . . . This consists of a number of hydraulic cylinders 6a, 6b, 6c,. . . corresponding to the number of ejection pins, which cylinders areattached to a frame 7 and are thus mechanically inter-connected. Thecylinders 6a, 6b, 6c, . . . communicate via ducts 4a, 4b, 4c, . . . withthe respective cylinders 3a, 3b, 3c, . . . .

Each cylinder 6a, 6b, 6c, . . . has its own piston 17a, 17b, 17c, . . .and piston rod 8a, 8b, 8c, . . . . Between these piston rods and theupper, moving half 1b of the tool 1 is an operative connection such thatthe piston rods 8a, 8b, 8c, . . . are influenced by the opening andclosing movements of the half 1b of the tool, in conjunction with whichthe movements of the piston rods 8a, 8b, 8c, . . . are transmitted bymeans of an incompressible fluid to the ejection pins 2a, 2b, 2c, . . .so that these move in an ejection direction when the tool 1 is opened.The pistons 16a, 16b, 16c, . . . and 17a, 17b, 17c, . . . are alsoinfluenced in accordance with the invention by a spring force acting inthe direction of ejection. The transmission of movement and the springforce are executed differently in the case of the preferred embodimentof the invention in accordance with FIGS. 1a, 1b, 1c, . . . , which isdescribed first, than in the case of the alternative embodiment inaccordance with FIGS. 2a, 2b, 2c, . . . .

In FIG. 1c, which may be taken as representing the constituent hydrauliccomponents of the arrangement in accordance with FIGS. 1a, 1b, thepiston 17 is of the plunger type, for which reason the connection of theduct 4 can be positioned in any desired fashion, and the piston rod 8 issealed against the cylinder 6 by means of a seal 18. The piston rod andits associated piston 16 for the ejection pin 2 are sealed against thecylinder 3 by means of seals 19 and 20. The cylinder 6, the duct 4, anda space 21 in the cylinder 3, which is defined not only by the piston 16and the cylinder wall, but also by the end wall 22 in which the seal 19for the piston rod is arranged, are filled with an incompressible fluid,which has been marked in FIG. 1c by a pattern of broken lines. The duct4 is connected to the cylinder 3 in an area in the vicinity of the seal19 so that the flow of fluid through it will not be disturbed bymovements of the piston 16. The aforementioned spring force acting inthe direction of ejection is generated by a compressible fluid enclosedin a space 23 which is defined by the piston 16, the walls of thecylinder 3 and the end wall 24 opposite the end wall 22. Theaforementioned operative connection between the tool half 1a and thepiston rods consists of a sheet 13, to which the ends of theaforementioned piston rods are attached, and an elongated device 14projecting from the aforementioned tool half, which device is soarranged as to push the sheet 13 downwards during the pressingoperation. In this way the piston rods with their plunger pistons 17 arepushed into their respective cylinder and force fluid via the respectiveduct 4 into the respective space 21. During compression of thecompressible fluid in the space 23, the piston 16 is pushed inwards intothe cylinder 3 so that the ejection pin 2 is caused to lie on a levelwith the press surface of the press tool 1.

When the tool 1 is opened after a pressing operation has been completed,the upper half 1a of the tool will move upwards, in conjunction withwhich the pushing down of the sheet 13 via the elongated device 14 willcease. Under the effect of the spring force on the compressed fluidenclosed in the space 23, the pistons 16 are forced upwards and theejection pin 2 ejects the pressed component 15. At the same time fluidis forced out of the space 21 via the duct 4 to the cylinder 6. Afterintroducing a new sheet blank for pressing in the tool 1, the proceduredescribed above is repeated.

In FIG. 2c, which may be taken as representing the constituent hydrauliccomponents of the arrangement in accordance with FIGS. 2a, 2b, thepiston 17 is sealed against the wall of the cylinder 6 by means of aseal 25, and the piston 16 has the seal 20, as before. There are noseals, however, between the piston rod 8 and the cylinder 6 and betweenthe ejection pin 2 and the cylinder 3. The spaces 23 and 26 between thepistons 16 and 17 and the corresponding uninterrupted end walls 24 and27 communicate via the duct 4 and are filled with an incompressiblefluid, which, as before, has been marked as a pattern of broken lines.The connections of the duct to each cylinder 3, 6 are situated close tothe uninterrupted end wall 24, 27 so as not to obstruct the fluid flowthrough the duct 4.

With reference to FIGS. 2a and 2b the piston rods 8a, 8b, 8c, . . . areconnected by means of a yoke 9 which is operatively connected to acompressive gas spring 10 acting between the yoke and the frame 7. Theoperative connection between the yoke 9 and the piston rod 11 of the gasspring 10 consists of rods 12 which are mounted in the frame 7 in such away that they are free to slide, said rods connecting the yoke 9 to asheet 28 against which the piston 10 is in contact.

The elongated device 14 which projects from the upper tool half 1a is soarranged in a similar fashion to the embodiment in accordance with FIG.1 as to push the sheet 28 downwards during the pressing operation,against the effect of the gas spring 10, see FIG. 2a, and as to leavethe sheet 28 unactuated when the tool 1 is open, see FIG. 2b.

The ejection arrangement in accordance with FIGS. 2a, 2b and 2c operatesin the following way: In FIG. 2a, which shows the press tool 1 during apressing operation, the sheet 28 is pushed down as far as a bottom endposition by the elongated device 14 against the effect of the gas spring10. Because the sheet 28 and the yoke 9 are connected to one another viathe rods 12, the yoke 9 will accordingly also be caused to be pusheddown as far as its bottom end position, and in so doing to pull down thepiston rods 8a, 8b, 8c, . . . . The negative pressure which is thusproduced inside the cylinders 6a, 6b, 6c . . . , in this way passes viathe ducts 4a, 4b, 4c, . . . to the corresponding cylinders 3a, 3b, 3c, .. . , which means that the ejection pins 2a, 2b, 2c, . . . are drawninto the respective cylinder so that the tips of the pins lie on thesame plane as the press surface.

On completion of a pressing operation the upper half 1a of the toolmoves upward together with the elongated device 14, in conjunction withwhich the action of the latter on the sheet 28 gradually ceases. Underthe effect of the gas spring 10 the sheet 28 is accordingly pushedupwards as far as its upper end position, as shown in FIG. 2b. The yoke9 accordingly also moves upwards and forces the piston rods 8a, 8b, 8c,. . . into their respective cylinders 6a, 6b, 6c, . . . . The positivepressure which is thus produced inside the cylinders passes via theducts 4a, 4b, 4c, . . . to the corresponding cylinders 3a, 3b, 3c, . . ., which means that the ejection pins 2a, 2b, 2c, . . . are pushed out,in conjunction with which a newly pressed component 15, see FIG. 2b, isejected from the lower part 1b of the tool. It will be appreciated that,by adjusting the relative position of a hydraulic cylinder, the startingposition of the appropriate ejection pins can be varied.

In the embodiment of the invention described above all the hydrauliccylinders are identical, which is of advantage with regard to theavailability of spare parts. This has been made possible by the factthat the cylinders 6a, 6b, 6c, . . . and the gas spring 10 act inopposite directions and interact via the operative connection, whichconsists of the yoke 9, the rods 12 and the sheet 28. As an alternativeembodiment within the scope of the idea of invention the cylinders 6a,6b, 6c, . . . and the gas spring 10 can be caused to act in the samedirection, although the piston rods 8a, 8b, 8c, . . . in this case aresealed against their respective cylinder, as in the embodiment inaccordance with FIGS. 1a, 1b and 1c, and the connection of the hoses 4a,4b, 4c, . . . is arranged close to the aforementioned seals.

Not only the cylinders 3a, 3b, 3c, . . . , but also the cylinders 6a,6b, 6c, . . . and the gas spring 10 are preferably provided withexternal threads and are screwed into the half 1b of the tool and intothe frame 7 and are secured with a nut. The possibility is afforded inthis way of adjusting the aforementioned units relative to one anotherfor the purpose of achieving full synchronism between the ejection pins2a, 2b, 2c . . . .

We claim:
 1. An assembly for the ejection of a pressed component from apress tool in a predetermined direction after completion of a pressingoperation, said press tool including a moving section and a secondsection, said moving section and second section adapted to separate at apress surface, said assembly comprising a plurality of ejection pinslocated within said second section and distributed over said presssurface each of said ejection pins having an end thereof located nohigher than said press surface during a pressing operation of said presstool, each said ejection pin end adapted to eject a component from saidpress tool after completion of a pressing operation, characterized inthat each ejection pin is operatively connected with an ejection pistonrod to a hydraulic ejection piston, said hydraulic ejection pistonaxially movably disposed in a hydraulic ejection cylinder having anejection cylinder wall, said ejection cylinder including an ejectionspace defined by said ejection piston and said ejection cylinder wall,said ejection space filled with an incompressible fluid, said ejectionspace being in open communication with a duct and a drive means fordriving said ejection pins, said drive means comprising a plurality ofmechanically inter-connected hydraulic drive cylinders includingassociated drive pistons and drive piston rods corresponding to saidplurality of ejection pins, said drive piston rods adapted to move insynchronism with the moving section of the press tool, and a resilientmeans for urging said drive pistons and ejection pistons into saidpredetermined direction.
 2. The assembly according to claim 1, includingmeans for adjusting the positions of said ejection and drive cylindersrelative to a fixed reference whereby the movement of said ejection pinsmay be sychronized.
 3. The assembly according to claim 1, characterizedin that each said ejection space is further defined by a first end wallof said ejection cylinder, a seal disposed in each said ejection spaceand sealingly engaged with a said ejection piston rod, a said ductconnected to each said hydraulic ejection cylinder in an area close tosaid seal, said drive pistons comprising plunger type pistons, and saidresilient means comprising a gas spring which includes a compressiblefluid confined within a spring space, said spring space defined by saidejection piston, said ejection cylinder wall, and a second end wall ofsaid ejection cylinder.
 4. The assembly according to claim 1,characterized in that said ejection space is further defined by an endwall of said ejection cylinder, each said duct being connected to arespective drive cylinder of said drive means at a location near a saidrespective end wall of each respective ejection cylinder, the outer endsof said piston drive rods attached to a yoke, said resilient meansconnected between said yoke and said drive cylinders whereby, when saidpress tool is opened, said drive pistons are pushed into each said drivecylinder so that a pressed component is ejected by said ejection pins,and so that, during a pressing operation, said ejection pins are movedtoward said press surface.
 5. The assembly according to claim 1 whereinsaid resilient means comprises a cylinder filled with a compressiblefluid.
 6. The assembly according to claim 1 wherein said resilient meanscomprises a spring.